LCOV - code coverage report
Current view: top level - include/linux - jhash.h (source / functions) Hit Total Coverage
Test: landlock.info Lines: 54 54 100.0 %
Date: 2021-04-22 12:43:58 Functions: 3 3 100.0 %

          Line data    Source code
       1             : #ifndef _LINUX_JHASH_H
       2             : #define _LINUX_JHASH_H
       3             : 
       4             : /* jhash.h: Jenkins hash support.
       5             :  *
       6             :  * Copyright (C) 2006. Bob Jenkins (bob_jenkins@burtleburtle.net)
       7             :  *
       8             :  * https://burtleburtle.net/bob/hash/
       9             :  *
      10             :  * These are the credits from Bob's sources:
      11             :  *
      12             :  * lookup3.c, by Bob Jenkins, May 2006, Public Domain.
      13             :  *
      14             :  * These are functions for producing 32-bit hashes for hash table lookup.
      15             :  * hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
      16             :  * are externally useful functions.  Routines to test the hash are included
      17             :  * if SELF_TEST is defined.  You can use this free for any purpose.  It's in
      18             :  * the public domain.  It has no warranty.
      19             :  *
      20             :  * Copyright (C) 2009-2010 Jozsef Kadlecsik (kadlec@netfilter.org)
      21             :  *
      22             :  * I've modified Bob's hash to be useful in the Linux kernel, and
      23             :  * any bugs present are my fault.
      24             :  * Jozsef
      25             :  */
      26             : #include <linux/bitops.h>
      27             : #include <linux/unaligned/packed_struct.h>
      28             : 
      29             : /* Best hash sizes are of power of two */
      30             : #define jhash_size(n)   ((u32)1<<(n))
      31             : /* Mask the hash value, i.e (value & jhash_mask(n)) instead of (value % n) */
      32             : #define jhash_mask(n)   (jhash_size(n)-1)
      33             : 
      34             : /* __jhash_mix -- mix 3 32-bit values reversibly. */
      35             : #define __jhash_mix(a, b, c)                    \
      36             : {                                               \
      37             :         a -= c;  a ^= rol32(c, 4);  c += b;     \
      38             :         b -= a;  b ^= rol32(a, 6);  a += c;     \
      39             :         c -= b;  c ^= rol32(b, 8);  b += a;     \
      40             :         a -= c;  a ^= rol32(c, 16); c += b;     \
      41             :         b -= a;  b ^= rol32(a, 19); a += c;     \
      42             :         c -= b;  c ^= rol32(b, 4);  b += a;     \
      43             : }
      44             : 
      45             : /* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */
      46             : #define __jhash_final(a, b, c)                  \
      47             : {                                               \
      48             :         c ^= b; c -= rol32(b, 14);              \
      49             :         a ^= c; a -= rol32(c, 11);              \
      50             :         b ^= a; b -= rol32(a, 25);              \
      51             :         c ^= b; c -= rol32(b, 16);              \
      52             :         a ^= c; a -= rol32(c, 4);               \
      53             :         b ^= a; b -= rol32(a, 14);              \
      54             :         c ^= b; c -= rol32(b, 24);              \
      55             : }
      56             : 
      57             : /* An arbitrary initial parameter */
      58             : #define JHASH_INITVAL           0xdeadbeef
      59             : 
      60             : /* jhash - hash an arbitrary key
      61             :  * @k: sequence of bytes as key
      62             :  * @length: the length of the key
      63             :  * @initval: the previous hash, or an arbitray value
      64             :  *
      65             :  * The generic version, hashes an arbitrary sequence of bytes.
      66             :  * No alignment or length assumptions are made about the input key.
      67             :  *
      68             :  * Returns the hash value of the key. The result depends on endianness.
      69             :  */
      70        5300 : static inline u32 jhash(const void *key, u32 length, u32 initval)
      71             : {
      72        5300 :         u32 a, b, c;
      73        5300 :         const u8 *k = key;
      74             : 
      75             :         /* Set up the internal state */
      76        5300 :         a = b = c = JHASH_INITVAL + length + initval;
      77             : 
      78             :         /* All but the last block: affect some 32 bits of (a,b,c) */
      79       51375 :         while (length > 12) {
      80       46075 :                 a += __get_unaligned_cpu32(k);
      81       46075 :                 b += __get_unaligned_cpu32(k + 4);
      82       46075 :                 c += __get_unaligned_cpu32(k + 8);
      83       46075 :                 __jhash_mix(a, b, c);
      84       46075 :                 length -= 12;
      85       46075 :                 k += 12;
      86             :         }
      87             :         /* Last block: affect all 32 bits of (c) */
      88        5300 :         switch (length) {
      89        1804 :         case 12: c += (u32)k[11]<<24;     fallthrough;
      90        1817 :         case 11: c += (u32)k[10]<<16;     fallthrough;
      91        1823 :         case 10: c += (u32)k[9]<<8;       fallthrough;
      92        1836 :         case 9:  c += k[8];             fallthrough;
      93        3499 :         case 8:  b += (u32)k[7]<<24;      fallthrough;
      94        3510 :         case 7:  b += (u32)k[6]<<16;      fallthrough;
      95        3521 :         case 6:  b += (u32)k[5]<<8;       fallthrough;
      96        3531 :         case 5:  b += k[4];             fallthrough;
      97        5237 :         case 4:  a += (u32)k[3]<<24;      fallthrough;
      98        5244 :         case 3:  a += (u32)k[2]<<16;      fallthrough;
      99        5258 :         case 2:  a += (u32)k[1]<<8;       fallthrough;
     100        5271 :         case 1:  a += k[0];
     101        5271 :                  __jhash_final(a, b, c);
     102        5271 :                  break;
     103             :         case 0: /* Nothing left to add */
     104             :                 break;
     105             :         }
     106             : 
     107        5300 :         return c;
     108             : }
     109             : 
     110             : /* jhash2 - hash an array of u32's
     111             :  * @k: the key which must be an array of u32's
     112             :  * @length: the number of u32's in the key
     113             :  * @initval: the previous hash, or an arbitray value
     114             :  *
     115             :  * Returns the hash value of the key.
     116             :  */
     117     5336653 : static inline u32 jhash2(const u32 *k, u32 length, u32 initval)
     118             : {
     119     5336653 :         u32 a, b, c;
     120             : 
     121             :         /* Set up the internal state */
     122     5336653 :         a = b = c = JHASH_INITVAL + (length<<2) + initval;
     123             : 
     124             :         /* Handle most of the key */
     125    56837415 :         while (length > 3) {
     126    51500762 :                 a += k[0];
     127    51500762 :                 b += k[1];
     128    51500762 :                 c += k[2];
     129    51500762 :                 __jhash_mix(a, b, c);
     130    51500762 :                 length -= 3;
     131    51500762 :                 k += 3;
     132             :         }
     133             : 
     134             :         /* Handle the last 3 u32's */
     135     5336653 :         switch (length) {
     136     1646330 :         case 3: c += k[2];      fallthrough;
     137     3165408 :         case 2: b += k[1];      fallthrough;
     138     5336653 :         case 1: a += k[0];
     139     5336653 :                 __jhash_final(a, b, c);
     140     5336653 :                 break;
     141             :         case 0: /* Nothing left to add */
     142             :                 break;
     143             :         }
     144             : 
     145     5336653 :         return c;
     146             : }
     147             : 
     148             : 
     149             : /* __jhash_nwords - hash exactly 3, 2 or 1 word(s) */
     150         564 : static inline u32 __jhash_nwords(u32 a, u32 b, u32 c, u32 initval)
     151             : {
     152         564 :         a += initval;
     153         564 :         b += initval;
     154         564 :         c += initval;
     155             : 
     156         564 :         __jhash_final(a, b, c);
     157             : 
     158         564 :         return c;
     159             : }
     160             : 
     161         450 : static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval)
     162             : {
     163         450 :         return __jhash_nwords(a, b, c, initval + JHASH_INITVAL + (3 << 2));
     164             : }
     165             : 
     166             : static inline u32 jhash_2words(u32 a, u32 b, u32 initval)
     167             : {
     168             :         return __jhash_nwords(a, b, 0, initval + JHASH_INITVAL + (2 << 2));
     169             : }
     170             : 
     171         114 : static inline u32 jhash_1word(u32 a, u32 initval)
     172             : {
     173         114 :         return __jhash_nwords(a, 0, 0, initval + JHASH_INITVAL + (1 << 2));
     174             : }
     175             : 
     176             : #endif /* _LINUX_JHASH_H */

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